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Flashcards in Gap junctions/Electrical Synapses Deck (43):
1

What are gap junctions?

An array of intercellular channels for direct cell-to-cell communication.

2

What are gap junctions composed of?

Connexins

3

What type of current is used for cell-to-cell communication?

Ionic current

4

What leads to complex assemblies of subunits of gap junctions made?

Co-expression of connexins.

5

How are intercellular channels at gap junctions packaged?

Densely packed

6

What direction is signalling between cells using gap junctions?

Bidirectional

7

Give two examples were gap junctions are used?

Oocyte and granulosa cells.
Epithelial cells of the gut.

8

What organ are gap junctions found in?

They are ubiquitous (found everywhere)

9

Define "ubiquitous"?

Found throughout the body.

10

What happens if there is a change in connexin protein or genes?

Causes connexin-associated disease.
Many of these as GJ are important throughout the body.

11

What is the permeability of gap junctions?

They are permeable to:
inorganic ions (K, Na, Cl, HCO3)
Small organic (signalling) molecules (cAMP, IP3)
Dyes
Metabolites (glucose)

12

Describe the bystander effect that is mediated by the connexin?

When looking at tumorigenesis.
When intoxicating a cell with pro-drug it only kills that one cell while if gap junctions were used it kills off all bystander cells that has the toxic gene.

13

What is the synaptic transmission mediated by?

Chemicals

14

How many connexin genes are there?

20 different connexin genes

15

Where are the connexin genes expressed? and by what type of cell?

Half are expressed in the brain.
Most by glia cells.

16

What is the most important protein when looking at electrical synapses?

Cx36

17

Name the two types of synapse transmission?

Chemical synapse.
Electrical synapse.

18

What is the difference between chemical and electrical synapse?

Chemical: using a transmitter (no direct contact)
Electrical: without transmitter (direct contact to transfer tonic current)

19

Assaying function of electrical synapses?

Specificity between different types.
Once applied cannot be reused

20

Name the 3 characteristics of electrical synaptic transmission?

Can pass sub threshold current
Strongly postsynaptic responses
Bidirectional

21

What is required for electrical transmission?

Ionic current

22

Time difference between electrical and chemical transmission?

Electrical activate faster than chemical ones.
Synaptic delay

23

Direction of release between electrical and chemical transmission?

Electrical almost always bidirectional.
Chemical not.

24

Polarisation specificity between electrical and chemical transmission?

Chemical are de/hyperpolarising.
Electrical not specificity.

25

Reliability between electrical and chemical transmission?

Electrical are reliable.
Chemical reliability varies.

26

Metabolically expenditure between electrical and chemical transmission?

Chemical uses more energy than electrical.

27

How would you test the electrical synapses?

Use gap junctions to look at the fast transmission between neurones.
Knockout the specific gene

28

How would you test the chemical synapses?

Look at the morphology and protein associated with vesicle docking and release.

29

Name the 6 properties that are important when looking at synapses?

1. Bidirectionality.
2. Shorter synaptic delay.
3. Sign preservation.
4. Mediated both hyper polarising and depolarising responses.
5. Facilitates synchrony and promotes AP.
6. Coordinates activity in cell-to-cell fashion.

30

What kind of network is created by electrical synapses?

Synchronously coactive neurones.

31

What does Cx36 do?

Creates multiple groups of coupled interneurones.
Restricted to interneurones.
Couples similar subtypes.
Creates homocellular assemblies.

32

Name the two different expression of connexins?

Homomeric
Heteromeric

33

Cx36 is vital for generating?

Synchrony generates brain rhythms

34

What are electrical synapse vital for in the cerebellum?

Important in neural circuits.

35

How are the inferior olivary nucleus important in motor impairment?

Neurones in this area generate sub threshold rhythms
Which occasionally trigger APs.
Send signals to the cerebellum.

36

How are the Cx36 linked to the inferior olivary nucleus that is necessary for motor impairment?

The membrane rhythms in neurones of the olive are synchronised.
Requires electrical synapses. Thus requires Cx36

37

Define "ataxia"?

When muscle contractions are impaired.

38

What protein is most electrical synapses comprised of?

Cx36.

39

What other things play a role in comprising the electrical synapses?

Other connexins and pannexins.

40

What are the electrical synapses in the retina comprised of?

Other connexins.

41

What passes through the electrical synapses?

Usually allows ionic current and small organic molecules.
Both directions.

42

What is the role of the electrical and chemical synapses?

Together generate complex electrical activity that encodes brain function.

43

Name 2 process that Cx36 is important in?

Brain retina and pancreas